Personal air sampling pump

ABSTRACT

A lightweight, portable air pump employing a solenoid driven rubber diaphragm and rubber flapper check valves to control inlet and outlet flow. The diaphragm has a flexible annulus and a rigid central section so that there is virtually no accommodation to load, used with independently timed drive pulses for essentially constant flow with varying load.

United States Patent [1 1 Guggenheim et a1.

[ 1 PERSONAL AIR SAMPLING PUMP [75] Inventors: S. Frederic Guggenheim,Teaneck,

N.J.; Robert T. Graveson, Briarcliff Manor, NY.

[73] Assignee: The United States of America as represented by the UnitedStates Atomic Energy Commission, Washington, DC.

[22] Filed: Apr. 17, 1973 [21] Appl. No.: 351,894

[52] US. Cl. 417/413 [51] Int. Cl. F04b 17/00 [58] Field of Search417/413 [56] References Cited UNITED STATES PATENTS Randolph .7 417/4131 1 June 4,1974

2,814,429 11/1957 Buchanan 417/413 3,273,505 9/1966 Miles et a1. 417/4133.410.059 11/1968 Garnier t v l l 417/413 $572,980 3/1971 Hollyday417/413 Primary Examiner-C. J. Husar Attorney, Agent, or FirmJohn A.Horan; Leonard Belkin [57] ABSTRACT A lightweight, portable air pumpemploying a solenoid driven rubber diaphragm and rubber flapper checkvalves to control inlet and outlet flow. The diaphragm has a flexibleannulus and a rigid central section so that there is virtually noaccommodation to load, used with independently timed drive pulses foressentially constant flow with varying load.

4 Claims, 4 Drawing Figures PERSONAL AIR SAMPLING PUMP BACKGROUND OF THEINVENTION The invention described herein was made in the course ofemployment by the U. S. Atomic Energy Commission.

The airborne contaminants a worker breathes, especially in mines andsimilarly confined locations. are the subject of growing concern towhich a great deal more attention is being paid.

. Efforts to monitor these contaminants so as to identify them andmeasure the extent of their presence involve generally the collection ofsamples from the air being breathed by the workers. One way to collectthe particulates for study is to draw air through a filter in thebreathing zone with a pump which would be packaged with its motor andpower supply. Such an assembly could be clipped to the workers belt anda hose could connect the pump to the filter holder on the brim on thesafety helmet.

In a typical device of this type, as the particulate accumulates on thefilter there is an increasing load on the motor and pump which resultsin a steady decline in the rate of air flow through the system. Aconsequence of this characteristic is that a measurement of total airflow over a given period of time computed from the length of operationof the pump is unreliable. For example, pumps in current use show a verymarked change in air flow, e.g. i 18 percent, with varying backpressure, e.g. 2 to 30 inches of water, so that additional equipment isrequired to obtain reliable information as the total amount of air drawnthrough the filter.

Other difficulties associated with previously designed equipment of thisnature have to do with their cost, ability to withstand general abuseand hostile environmental conditions, and general lack of care as mightbe expected from the worker carrying such a device.

SUMMARY OF THE INVENTION The present invention overcomes many of thedisadvantages of present portable air sampling pumps by providing acompact, lightweight arrangement in which a disphragm is reciprocated ata constant repetition rate and stroke, and check valves are provided topermit intake and exhaust to occur, the check valves being designedespecially to minimize leakage when closed. The swept volume per strokeis relatively constant. The diaphragm is provided with a large rigidsection and a narrow flexible annulus so that there is no accommodationto the pressure load, that is, the back pressure. The results of theunique construction include a lightweight device which is thoroughlyrugged though simple and economic to make and operate, and yet, over aback pressure which varies from 2 to 20 inches of water the BRIEFDESCRIPTION OF THE DRAWING FIG. 1 is an elevation view in section of apreferred embodiment of the invention.

FIG. 2 shows details of a valve.

FIG. 3 shows details of a valve seat facing.

FIG. 4 shows a section along 4-4 of F IG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figures,portable air sampling pump 10 consists of a cylindrical tube 12 in whichall of the components of pump 10 are held together by a pair ofretaining rings 14 and 16. Adjacent retaining ring 14 is an inlet/outletplug 18 which is provided with an air inlet opening 22 therethrough toaccommodate spud or pipe 24 and an exhaust opening 26 which maycommunicate by way of passageways 28 with exhaust ports 32 distributedcircumferentially through the wall of cylin der 12. Opening 26, as willbe noted later, is large enough to accommodate a flap element to belater described.

Pumping chamber 34 within cylindrical tube 12 is formed on one side of adiaphragm 36. A disc 38, held in place by a ring 42, shown in greaterdetail in FIG. 2, is made from a pliant material such as rubber andincludes a pair of inlet and exhaust flap elements 44 and 46,respectively, formed by casting through disc 38 U- shapedconfigurations, as illustrated.

A pair of facings 48 and 52, similarly of suitable pliant material suchas rubber, sandwich disc 38. As best shown in FIG. 3, facing 48 isprovided with a first opening 54 which is aligned with opening 22 ofplug 18 and flap element 44 of disc 38. The size of opening 54 is suchas to permit flap element 44 to overlap same to a substantial degree.Facing 48 is provided with a second opening 56 which is also largeenough to accommodate free movement of exhaust flap element 46 andpermit relatively unimpeded air flow as shown by the arrows illustrated.A cantilever spring 57, embedded at one end in facing 48 as illustrated,or, if desired, adhered to the surface of facing 48 adjacent disc 38,extends into the opening 56 to act as a spring for flap element 46,biasing the latter against facing 52, sealing opening 62. In a similarfashion, facing 52 is provided with a large opening 58 to accommodateinlet flap element 44, a cantilever spring 59 adhered to facing 52 tobias element 44 against facing 48, and a smaller opening 62 overlappedby exhaust flap element 46.

Pump head 64 forming the opposite end of chamber 34 clamps on one sidedisc 38 and plug 18 the other side of pump head 64 provides one supportfor diaphragm 36. Head 64 is provided with suitable openings asillustrated to permit unimpeded air flow in the manner described.Facings 48 and 52 are adhered in suitable manner respectively, to plug18 and pump head 64.

Diaphragm 36 is made from pliant material such as rubber and is providedwith a flange 66 which is held in place by a retainer ring 68, pump head64, and a solenoid head 72. It will be noted that the central region ofdiaphragm 36 is rendered rigid by a pair of rigid discs 74 and 76mounted on opposite sides thereof leaving only a narrow annular region78 which is flexible. For the purposes of this invention the radialwidth of the annular region 78 should be no more than about 30 openingto weight, portable pump 3 percent of the radius of diaphragm 36, tomaintain uniform pumping flow as buildup on the filter occurs.

Filling the remaining space within cylinder 12 is sole noid 82 having acoil 83, a slidable core 86 and a stationary core 88 with a spring 92biasing the former to the left. Slidable core 86 is connected by way ofa coupling 94 to diaphragm 36 and discs 74 and 76 through the use of aretaining ring 96 and a spring retaining ring 98. The pump stroke is notadjustable and is determined by the left end stop, when disc 74 strikespump head 64 and the right end stop when core 86 strikes stationary core88. A closure plug 102 having a threaded accommodate a screw 104 incontact with solenoid 82 as illustrated holds the latter'in place. Apair of leads 106 and 108 deliver electric power to coil 83. In theposition illustrated, coil 83 is deenergized and core 86 is in theexhaust stroke by virtue of the action of spring 92, causing flapperelement 46 to be open to permit exhaust whereas flapper element 44 isclosed against incoming flow.

When a pulse of electrical energy is delivered by way of leads 106 and108 to coil 83, core 82 is retracted to the right, moving the centralregion of diaphragm 36 to the right, causing flapper element 46 toclose, and flapper element 44 to open, permitting air to enter intochamber 34. Electrical pulses are delivered from a battery source and atiming circuit, not shown, at a uni form rate independent of the load onpump 1050 that the repetition rate is not affected thereby. Any suitableportable power source and a timing circuit as known in the art fordelivering electrical pulses at a uniform rate would be satisfactory forpurposes of this invention, or if desired, a stationary source may beemployed, with a lead line extending to the person carrying pump 10.Because of the lightweight and efficient design of pump 10, only arelatively small amount of electrical power is required. An example of apower source which has been employed successfully is a nickel cadmiumbattery, Gould alkaline No. 400703, 12 V 225 ma hours, and a timingcircuit as described in IEEE second lnternational GeoscienceSymposiumDigestof Technical Papers, Washington; through 17-4, "Impulse DriveRecorder" by S. Frederic Guggenheim and Norman Latner.

In the operation of the apparatus described, diaphragm 36 isreciprocated at a uniform rate by solenoid 82, air entering chamber 34through inlet pipe 24 and opening 54 in facing 48 during suction withdiaphragm 36 retracted to the right and exhaust flapper element 46closed by the combination of suction and the action of cantilever spring57, and air then exhausted through opening 62 during the reverse strokeof diaphragm 36 as illustrated.

Cantilever springs 57 and 59 insure that there is rapid and completeclosure of flapper elements 46 and 44, while the substantial overlappingof the latter elements of the facing surfaces surrounding openings 62and 54 and their construction of pliant material insure that there is aminimum of leakage. These features all contribute to the effectivenessof the pump.

it is thus seen that there has been provided a lightof economic'andpractical construction. The diaphragm acts like a piston with all of.

D.C'., Apr. 14-17., 1970, pp'lT-l.

its advantages but at the same time it is light in weight I and mass,requires fewer moving parts and has no leakage past its sides. The wholeassembly of the pump requires only four snap rings and one screwassembled inside of a cylinder so that it is simple and inexpensive tomake and to maintain and is resistant to rough usage in the field underadverse conditions. The valves provide for rubber to rubber contact anddue to their light weight and mass they open and close rapidly withvirtually no leakage after closing. I

, Another feature of this invention is the use of positive stopsat theend of each stroke of diaphragm 36. Therefore, the volume swept at eachstroke is constant. The pump air volume delivery may be varied only byshortening or lengthening the time between strokes (changing the pulsefrequency of the electronic circuit). The electrically powered stroke tothe right is at high speed (about 30 to 50 milliseconds). This strokeinstantaneously creates a partial vacuum between the pump and the filterthat is upstream of inlet pipe 24, and in the elapsed time to the nextintake stroke, air

flows through the filter to relieveor reduce the vacuumand restoreessentially atmospheric pressure between the filter and a minimumelapsed time between pump power strokes. It is an essential concomitantto the maintenance of constant volume air flow with increasing pressuredrop across the filter.

What is claimed:

1. A compact, lightweight gas pump for delivering said gas at asubstantially constant flow rate over a wide range of back pressurecomprising:

a. first and second wall means forming therebetween a chamber;

b. said first wall means having a rigid central section and a flexibleannular section;

0. said second wall means having formed therein a pair of inlet andoutlet flap elements;

d. first and second valve walls adjacent opposite sides of said secondwall means, said first valve wall being within said chamber and havingan exhaust opening controlled by the outlet flap element and an openingto permit inlet flow, and said second valve wall having an inlet openingcontrolled by the inlet flap element and an opening to permit exhaustflow;

e. means in said first and second walls for biasing said flap elementsinto closing their respective inlet and exhaust openings; and

f. means for reciprocating said rigid central section of said first wallmeans to cause exhaust of said gas as said first wall means moves towardsaid second wall means and intake of said gas as said first wall meansmoves away from said second wall means.

' 2. The pump of claim 1 in which mechanical stops are provided to limitthe stroke of said first wall means in each direction.

3. The pump of claim 2 in which the radial width of said flexibleannular section is no more than 30 percent of the radius of said firstwall means.

4. The pump of claim 3 in which second wall means and said first andsecond valve walls are made from pliant material.

1. A compact, lightweight gas pump for delivering said gas at asubstantially constant flow rate over a wide range of back pressurecomprising: a. first and second wall means forming therebetween achamber; b. said first wall means having a rigid central section and aflexible annular section; c. said second wall means having formedtherein a pair of inlet and outlet flap elements; d. first and secondvalve walls adjacent opposite sides of said second wall means, saidfirst valve wall being within said chamber and having an exhaust openingcontrolled by the outlet flap element and an opening to permit inletflow, and said second valve wall having an inlet opening controlled bythe inlet flap element and an opening to permit exhaust flow; e. meansin said first and second walls for biasing said flap elements intoclosing their respective inlet and exhaust openings; and f. means forreciprocating said rigid central section of said first wall means tocause exhaust of said gas as said first wall means moves toward saidsecond wall means and intake of said gas as said first wall means movesaway from said second wall means.
 2. The pump of claim 1 in whichmechanical stops are provided to limit the stroke of said first wallmeans in each direction.
 3. The pump of claim 2 in which the radialwidth of said flexible annular section is no more than 30 percent of theradius of said first wall means.
 4. The pump of claim 3 in which secondwall means and said first and second valve walls are made from pliantmaterial.